Embodiments of the present invention generally relate to systems and methods using an electrified projectile for reducing mobility in a person or animal.
Weapons that deliver electrified projectiles have been used for self defense and law enforcement where the target struck by the projectile is a human being or an animal. One conventional class of such weapons includes conducted energy weapons of the type described in U.S. Pat. Nos. 3,803,463 and 4,253,132 to Cover. A conducted energy weapon typically fires two projectiles from a handheld device to a range of about 15 feet to deliver a stimulus signal to the target. The projectiles remain tethered to a power supply in the handheld device by two fine, insulated wires. Tethered projectiles are also called darts.
A stimulus signal comprising a series of relatively high voltage pulses are delivered through the wires and into the target, causing pain in the target. At the time that the stimulus signal is delivered, a high impedance gap (e.g., air or clothing) may exist between electrodes of the projectiles and the target's conductive tissue. The stimulus signal conventionally includes a relatively high voltage (e.g., about 50,000 volts) to ionize a pathway across such a gap of up to 2 inches. Consequently, the stimulus signal may be conducted through the target's tissue without penetration of the projectile into the tissue. Effectiveness of a stimulus signal of the type described by Cover is limited. For example, tests showed that most human targets who were given a physical motor task to perform during or after being struck with the projectiles and subjected to a relatively high voltage (e.g., fight against the person armed with the weapon) could accomplish the task.
Conventional conducted energy weapons that use a gunpowder propellant have limited application. These weapons are classified as firearms and are subject to heavy restrictions in the United States, severely limiting their marketability.
Other conventional energy weapons known as stun guns omit the projectiles and deliver essentially the same stimulus signal to a target when the target is in close proximity to the weapon. These weapons have limited application because close proximity typically decreases the safety of the person armed with the weapon.
Another conventional conducted energy weapon, not classified as a firearm, uses compressed gas to propel the projectile as described for example in U.S. Pat. No. 5,078,117 to Cover. This propulsion system uses a relatively small primer that is detonated by an electric charge in the weapon. The detonation forces a cylinder of compressed gas such as nitrogen onto a puncturing device to release an amount of compressed nitrogen that propels the projectile out of the weapon.
More recently, a relatively higher energy waveform has been used in the conducted energy weapons discussed above. This waveform was developed from studies using anesthetized pigs to measure the muscular response of a mammalian subject to an energy weapon's stimulation. Devices using the higher energy waveform are called Electro-Muscular Disruption (EMD) devices and are of the type generally described in U.S. patent application Ser. No. 10/016,082 to Patrick Smith, filed Dec. 12, 2001, incorporated herein by this reference. An EMD waveform applied to an animal's skeletal muscle typically causes that skeletal muscle to violently contract. The EMD waveform apparently overrides the target's nervous system's muscular control, causing involuntary lockup of the skeletal muscle, and may result in complete immobilization of the target. Unfortunately, the relatively higher energy EMD waveform is generally produced from a higher power capability energy source. For instance, a weapon of this type may include 8 AA size 1.5 volt batteries, a large capacity capacitor, and transformers to generate a 26-watt EMD output to a tethered projectile (e.g., a dart).
A two pulse waveform of the type described in U.S. patent application Ser. No. 10/447,447 to Magne Nerheim filed Feb. 11, 2003, provides a relatively high voltage, low amperage pulse (to form an arc through a gap as discussed above) followed by a relatively lower voltage, higher amperage pulse (to stimulate the target). Effects on skeletal muscles may be achieved with 80% less power than EMD waveforms, discussed above.
Conventional conducted energy weapons have limited range to achieve an effective separation of two electrodes to stimulate the target by an electric current passing between the electrodes. In one conventional weapon, two projectiles, each with an electrode, are fired from the same cartridge at an 8-degree angle of separation. The upper projectile is fired along the line of sight from the weapon. The lower projectile is fired at an 8-degree downward angle. This angle separates the electrodes during flight. At a range of 21 feet, the bottom electrode will contact the target about 3 feet below the top electrode's point of contact.
A consistent electrode separation regardless of the distance from the handheld device to the target is provided in a system as described in U.S. Pat. No. 6,575,073 to McNulty. There, a larger projectile carrying a first electrode includes a range sensor. At a sensed distance from the target, the larger projectile fires a smaller projectile carrying the second electrode. Higher cost and lower reliability result. A range sensing system could malfunction by having a narrow field of view, for example, where the device could impact the target at such an oblique angle that the range sensor never effectively senses the target until it is too close to effectively deploy the second electrode. Alternatively, if the device is fired in a direction where the projectile must pass close by an obstacle en route to the target, the range sensor might detect an object next to its trajectory and prematurely fire the second electrode, causing the second electrode to miss the target.
An array of electrodes tethered together has been described in U.S. Pat. No. 5,698,815 to Ragner. Such arrays, when in flight, are inherently aerodynamically unstable. Accuracy of hitting a target with such an array is less than with other technologies discussed above.
Without systems and methods of the present invention, further improvements in cost, reliability, range, and effectiveness cannot be realized for energy weapons. Applications for energy weapons will remain limited, hampering law enforcement and failing to provide increased self defense to individuals.